Confocal microscopy with Cryostation – No drift at 3.5 K

Montana Instruments has just released its brand new option for confocal microscopy at low temperatures. With the new confocal microscope option, the sample can easily be focused to an unsurpassed accuracy, even at temperatures as low as 3.5 K. Drift of both the sample and the optic, even when cooling down the sample, is eliminated by a patented design.

Sample translation and focus is accomplished with built-in nano positioners. Temperatures of the high-resolution objectives and sample are controlled to an accuracy of 0.01 degrees for undetectable drift levels. The provided replacement power supply ensures performance.

The system is based on a vacuum-compatible Zeiss EC Epiplan-Neofluar 100 x objective with an infinity color-corrected image distance, a numerical aperture (NA) of 0.90 and 0.31 mm working distance. The field of view is 25 mm. The transmission spectrum will be provided upon request.

To demonstrate the system’s resolution, a 3D calibration grid was imaged. The system imaged the calibration grid with 14 pixels per 1.2 µm of the object or an effective pixel size of less than 0.1 µm.

The Cryostation microscopy option is the ideal tool to run confocal microscopy on single molecules with a cryostat with a closed helium circuit in an almost drift-free setup with a high numerical aperture.

Optical microscopy of individual quantum objects has been in the center of some of the most outstanding new developments in quantum physics during the past decade, especially in quantum information processing and quantum measuring technologies. Optical measurements at low temperatures are key to future discoveries.

Parameters for measuring

Time period

1 hour

Room temperature change

10 °C

Measuring result

Sample temperature change

< 10 mK

Sample drift

< 200 nm

The experiment demonstrates drift-free microscopic measurements on single molecules at 3.5 K. Samples are nitrogen vacancies (NV) in diamond, known to be dark single photon sources which can only be imaged with well corrected microscope objectives with the highest numerical aperture. The figure shows a schematic measurement setup.

The left figure shows a 20 x 20 µm view of a diamond structure with nitrogen vacancy centers. The right figure shows a magnified single dot. The typical drift is less than 200 nm in one hour.

Cryostation features easy access to the sample chamber. The microscope option also features easy user access for optical components and the sample chamber setup. Setup is easy: Lift off the housing, unbolt and remove the radiation shield, and both sample and wiring are freely accessible for changes.

Thermal and optical drift are known to correlate with ambient temperature changes. The system‘s temperature stability was tested in an experiment in which the room temperature was dropped by 10 °C for an hour. During this time, no significant changes were detected in neither the sample nor the objective temperature.

Left: A 3D grid was used for calibrationRight: The system has imaged the grid with 14&nbsp;pixels across the 1.2&nbsp;µm object, or an effective pixel size less than 0.1&nbsp;µm

Left: 20&nbsp;µm x 20&nbsp;µm view of a diamond structure with nitrogen vacanciesRight: Enlarged view of a single defect. Drift within one hour is below 200&nbsp;nm